1. Field of the Invention
The present invention relates to a composite thin-film magnetic head comprising a recording head and a reproducing head and a method of manufacturing such a thin-film magnetic head, and to a thin-film magnetic head material used for producing such a thin-film magnetic head and a method of manufacturing such a thin-film magnetic head material.
2. Description of the Related Art
Performance improvements in thin-film magnetic heads have been sought as surface recording density of hard disk drives has increased. Composite thin-film magnetic heads have been widely used. A composite head is made of a layered structure including a recording head having an induction magnetic transducer for writing and a reproducing head having a magnetoresistive (MR) element for reading. MR elements include an anisotropic magnetoresistive (AMR) element that utilizes the AMR effect and a giant magnetoresistive (GMR) element that utilizes the GMR effect. A reproducing head using an AMR element is called an AMR head or simply an MR head. A reproducing head using a GMR element is called a GMR head. An AMR head is used as a reproducing head whose surface recording density is more than 1 gigabit per square inch. A GMR head is used as a reproducing head whose surface recording density is more than 3 gigabits per square inch.
The performance of the reproducing head is improved by replacing the AMR film with a GMR film and the like with an excellent magnetoresistive sensitivity. Alternatively, a pattern width such as an MR height, in particular, may be optimized. The MR height is the length (height) between an end of the MR element closer to the air bearing surface and the other end. The MR height is controlled by an amount of lapping when the air bearing surface is processed. The air bearing surface is a surface of the thin-film magnetic head facing toward a magnetic recording medium and may be called a track surface, too.
Performance improvements in a recording head are also required as the performance of a reproducing head is improved. One of the factors that determine the recording head performance is a pattern width such as a throat height (TH), in particular. The throat height is the length (height) of portions of magnetic pole layers facing each other with a recording gap layer in between, between the air-bearing-surface-side end and the other end. A reduction in throat height is desired in order to improve the recording head performance. The throat height is controlled as well by an amount of lapping when the air bearing surface is processed.
It is required to increase the track density on a magnetic recording medium in order to increase recording density among the performance characteristics of a recording head. To achieve this, it is required to implement a recording head of a narrow track structure wherein the width of top and bottom poles sandwiching the recording gap layer on a side of the air bearing surface is reduced down to a submicron order. Semiconductor process techniques are utilized to implement such a structure.
As thus described, it is important to fabricate well-balanced recording and reproducing heads to improve the performance of a thin-film magnetic head.
Reference is now made to FIG. 38A to FIG. 46A, FIG. 38B to FIG. 46B, and FIG. 47 to FIG. 49 to describe an example of a manufacturing method of a composite thin-film magnetic head as an example of a manufacturing method of a related-art thin-film magnetic head. FIG. 38A to FIG. 46A are cross sections each orthogonal to the air bearing surface. FIG. 38B to FIG. 46B are cross sections each parallel to the air bearing surface of the pole portion.
According to the manufacturing method, as shown in FIG. 38A and FIG. 38B, an insulating layer 102 made of alumina (Al2O3), for example, having a thickness of about 5 xcexcm, is deposited on a substrate 101 made of aluminum oxide and titanium carbide (Al2O3xe2x80x94TiC), for example.
Next, as shown in FIG. 39A and FIG. 39B, on the insulating layer 102, a bottom shield layer 103 made of a magnetic material is formed for a reproducing head.
Next, as shown in FIG. 40A and FIG. 40B, on the bottom shield layer 103, alumina, for example, having a thickness of 40 to 70 nm, is deposited through sputtering to form a bottom shield gap film 104 as an insulating film. On the bottom shield gap film 104, an MR film of tens of nanometers in thickness is formed for making an MR element 105 for reproduction. Next, with a photoresist pattern as a mask, the MR film is etched through ion milling, for example, to form the MR element 105. The MR element 105 may be either a GMR element or an AMR element.
Next, as shown in FIG. 41A and FIG. 41B, a top shield gap film 106 as an insulating layer is formed on the bottom shield gap film 104 and the MR element 105. The MR element 105 is embedded in the shield gap films 104 and 106.
Next, as shown in FIG. 42A and FIG. 42B, on the top shield gap film 106, a top shield layer-cum-bottom pole layer (called a top shield layer in the following description) 107 is formed. The top shield layer 107 is made of a magnetic material and used for both a reproducing head and a recording head.
Next, a recording gap layer 108 made of an insulating film such as an alumina film is formed on the top shield layer 107. Next, the recording gap layer 108 is partially etched in a backward portion (the right side of FIG. 42A) to form a contact hole for making a magnetic path. Next, a top pole tip 109 for the recording head is formed on the pole portion of the recording gap layer 108. The top pole tip 109 is made of a magnetic material such as Permalloy (NiFe) or FeNx as a high saturation flux density material. The top pole tip 109 forms part of a top pole layer. At the same time, a magnetic layer 119 made of a magnetic material is formed for making the magnetic path in the contact hole for making the magnetic path.
Next, the recording gap layer 108 and the top shield layer (bottom pole layer) 107 are etched through ion milling, using the top pole tip 109 as a mask. As shown in FIG. 42B, the structure is called a trim structure wherein the sidewalls of the top pole layer (the top pole tip 109), the recording gap layer 108, and part of the top shield layer (bottom pole layer) 107 are formed vertically in a self-aligned manner. The trim structure suppresses an increase in the effective track width due to expansion of the magnetic flux generated during writing in a narrow track.
Next, as shown in FIG. 43A and FIG. 43B, an insulating layer 110 of alumina, for example, having a thickness of about 3 xcexcm is formed over the entire surface. The insulating layer 110 is polished to the surfaces of the top pole tip 109 and the magnetic layer 119 and flattened. The polishing method may be mechanical polishing or chemical mechanical polishing (CMP). The surfaces of the top pole tip 109 and the magnetic layer 119 are thereby exposed.
On the flattened insulating layer 110 a photoresist layer 111 is formed into a specific pattern through high-precision photolithography. Next, on the photoresist layer 111 a thin-film coil 112 of a first layer is made for the induction-type recording head. The thin-film coil 112 is made of copper (Cu), for example.
Next, as shown in FIG. 44A and FIG. 44B, a photoresist layer 113 is formed into a specific pattern on the photoresist layer 111 and the coil 112. Heat treatment is performed at a temperature of 250 to 300xc2x0 C., for example, to flatten the surface of the photoresist layer 113.
Next, as shown in FIG. 45A and FIG. 45B, a thin-film coil 114 of a second layer is formed on the photoresist layer 113. Next, a photoresist layer 115 is formed into a specific pattern on the photoresist layer 113 and the coil 114. Heat treatment is performed at a temperature of 250 to 300xc2x0 C., for example, to flatten the surface of the photoresist layer 115.
Next, as shown in FIG. 46A and FIG. 46B, a top yoke layer 116 for the recording head is formed on the top pole tip 109, the photoresist layers 111, 113 and 115 and the magnetic layer 119. The top yoke layer 116 is made of a magnetic material such as Permalloy. Next, an overcoat layer 117 of alumina, for example, is formed to cover the top pole layer 116. Finally, machine processing of the slider is performed to form the air bearing surface of the recording head and the reproducing head. The thin-film magnetic head is thus completed.
FIG. 47 and FIG. 49 show the completed thin-film magnetic head. FIG. 47 is a cross section of the head orthogonal to the air bearing surface 120. FIG. 48 is an enlarged cross section of the pole portion parallel to the air bearing surface 120. FIG. 49 is a top view of the head. The overcoat layer 117 is omitted in FIG. 49. In FIG. 47 the throat height is indicated with xe2x80x98THxe2x80x99 and the MR height is indicated with xe2x80x98MR-Hxe2x80x99. As shown in FIG. 48 and FIG. 49, a conductive layer 121 is provided on a side of the MR element 105.
In addition to the throat height and the MR height, another factor that determines the performance of a thin-film magnetic head is an apex angle as indicated with xcex8 in FIG. 47. The apex is a hill-like raised coil portion covered with the photoresist layers 111, 113 and 115. The apex angle is an angle formed between the top surface of the insulating layer 110 and the straight line drawn through the edges of the pole-side lateral walls of the apex.
The performance and characteristics of a thin-film magnetic head are mainly determined by the MR element of the reproducing head and the pole portion of the recording head. To be specific, the performance and characteristics of the reproducing head are mainly determined by the track width of the reproducing head, corresponding to the MR element width. The performance and characteristics of the recording head are mainly determined by the pole portion dimensions such as the throat height and the track width of the recording head. Therefore, the demands of customers of thin-film heads are concentrated on matters relating to the process of making the MR element of the reproducing head and the pole portion of the recording head, such as the track width of the reproducing head and the throat height and the track width of the recording head.
Therefore, in order to mass-produce thin-film magnetic heads that satisfy the specifications required by the customer, it is necessary that the manufacturing steps taken to fabricate the MR element and steps that follow should conform to the customer""s demands.
However, as described above with reference to FIG. 38A to FIG. 46A and FIG. 38B to FIG. 46B, the steps taken to fabricate the MR element belong to the early part of the entire steps of mass-producing thin-film heads, according to the related-art method. Therefore, the time required for steps taken to fabricate the MR element and steps that follow make up a great proportion of the time required for the entire steps in the related-art method. A long cycle time is therefore required in the related art. The cycle time is a period required between receipt of an order from the customer and completion and shipment of products conforming to the specifications required by the customer. The cycle time is about 20 to 25 days, for example. It is 30 to 40 days in some cases. Even though an agreement is made in an early stage between the customer and the manufacturer with regard to the specifications of thin-film heads such as performance characteristics, it takes many days to finally ship products.
These days technology advances at a remarkable rate and improvements are noticeable in surface recording density and reproduction rate required by the customer. Accordingly, modifications and improvements are made to the specifications of hard disk drives of computers every several months. Therefore, the customer demands that thin-film heads meeting the requirements be shipped in a short time after the order. The manufacturer is thus required to design products meeting the specifications required by the customer, mass-produce and ship the products in a short time.
Under such circumstances, it is difficult to satisfy the customer""s requests since a long cycle time is required in prior art.
Inspections are performed on complete thin-film heads after the entire manufacturing steps are finished in prior art. As a result, even if non-conforming heads are produced during the manufacturing steps, it is impossible to eliminate them. It is therefore difficult to improve yields of complete products.
In order to achieve high surface density recording, that is, to fabricate a recording head with a narrow track structure, techniques are required for obtaining a submicron-order top pole layer through the use of semiconductor process techniques. As the narrow track structure is obtained, it is desired that the pole is made of a magnetic material having higher saturation flux density.
However, it is difficult to reduce the size of the top pole layer since the top pole layer is formed on the apex, that is, a hill-like raised coil portion in the related-art thin-film magnetic head. This problem will now be described. As disclosed in Published Unexamined Japanese Patent Application Hei 7-262519 (1995), for example, frame plating may be used as a method for fabricating the top pole layer. In this case, a thin electrode film made of Permalloy, for example, is formed by sputtering, for example, to fully cover the apex. Next, a photoresist is applied on the electrode film and patterned through a photolithography process to form a frame to be used for plating. The top pole layer is then formed by plating through the use of the electrode film previously formed as a seed layer.
However, there is a difference in height between the apex and the other part, such as 7 to 10 xcexcm or more. The photoresist whose thickness is 3 to 4 xcexcm is applied to cover the apex. If the photoresist thickness is required to be at least 3 xcexcm on top of the apex, a photoresist film having a thickness of 8 to 10 xcexcm or more, for example, is formed below the apex since the fluid photoresist goes downward.
To implement a recording track width of the submicron order as described above, it is required to form a frame pattern of the submicron order through the use of a photoresist film. Therefore, it is required to form a fine pattern of the submicron order through the use of a photoresist film having a thickness of 8 to 10xcexcm or more. However, it is extremely difficult to form a photoresist pattern having such a thickness into a reduced pattern width in a manufacturing process.
Furthermore, rays of light used for exposure of photolithography are reflected off the base electrode film as the seed layer. The photoresist is exposed to the reflected rays as well and the photoresist pattern may be out of shape. It is therefore impossible to obtain a sharp and precise photoresist pattern.
As thus described, it is difficult in prior art to fabricate the top pole layer with accuracy if the pole width of the submicron order is required.
Therefore, as described above with reference to the steps of the related-art example shown in FIG. 42A to FIG. 46A and FIG. 42B to FIG. 46B, a method has been applied, too, (as disclosed in Published Unexamined Japanese Patent Application Sho 62-245509 [1987] and Published Unexamined Japanese Patent Application Sho 60-10409 [1985]), in which the track width of 1.0 xcexcm or less is obtained with the top pole tip 109 that is effective for making a narrow track of the recording head. The top pole layer 116 to be a yoke portion connected to the top pole tip 109 is then formed. In such a manner the ordinary top pole layer is divided into the top pole tip 109 and the top pole layer 116 to be the yoke portion. The top pole tip 109 of the submicron width that defines the track width is thereby formed on the flat surface on the recording gap layer 108.
However, the following problems are still found in such a thin-film magnetic head having a two-layer top pole layer that defines the track width.
The top pole layer 116 is aligned on top of the top pole tip 109 through alignment of photolithography. Therefore, if the top pole tip 109 and the top pole layer 116 are greatly shifted to one side when seen from the air bearing surface 120, writing could be performed on a side of the top pole layer 116 and the effective track width could be increased. As a result, so-called side write occurs in the thin-film magnetic head having the two-layer top pole layer, that is, data is written in a region where data is not supposed to be written.
Furthermore, a magnetic flux may saturate in the portion where the top pole tip 109 and the top pole layer 116 are in contact with each other since the top pole tip 109 and the top pole layer 116 are different in width. It is therefore impossible to improve the writing properties such as flux rise time.
In the thin-film magnetic head the throat height is defined by an end of the top pole tip 109 further from the air bearing surface 120. However, if the width of the pole tip 109 is reduced, rounded pattern edges are obtained through photolithography. Consequently, the throat height that is required to be precise is made uneven, and the yield is greatly reduced in the processing and lapping steps of the air bearing surface 120.
In the related-art head the coils 112 and 114 are formed after the MR element 105 is formed. Therefore, if the MR element 105 is a GMR element having a high sensitivity, in particular, the reading sensitivity of the MR element 105 could be reduced, due to the effect of heat treatment performed on the photoresist for making the coils 112 and 114 or the effect of water thereby produced.
Furthermore, a number of steps are required to complete the related-art head after the MR element 105 is formed. Therefore, if the MR element 105 is a GMR element having a plurality of very thin (about 1 to 5 nm) layers, in particular, damage of the MR element 105 such as static damage is likely to occur through handling and so on.
In prior art an overcoat layer of alumina, for example, whose thickness is about 30 to 40 xcexcm is formed to protect the reproducing head and the recording head and to maintain the quality of the product in a step immediately before the completion of the mass-production process of the thin-film magnetic heads. Consequently, warpage of the substrate results due to the thick overcoat layer or many particles are generated when the thick layer is formed through sputtering. The property and yields of the thin-film magnetic heads are thereby reduced. In prior art it takes fifteen hours or more to form the alumina film of about 40 xcexcm in thickness by sputtering. The cycle time of mass-production of the thin-film magnetic heads and the sputtering capability are therefore greatly limited.
It is a first object of the invention to provide a thin-film magnetic head and a method of manufacturing the same and a thin-film magnetic head material and a method of manufacturing the same for providing thin-film magnetic heads that meet specifications required by the customer in a short time and for improving yields of thin-film magnetic heads.
In addition to the first object, it is a second object of the invention to provide a thin-film magnetic head and a method of manufacturing the same and a thin-film magnetic head material and a method of manufacturing the same for reducing the track width of the recording head without reducing the performance characteristics and yields.
In addition to the first object, it is a third object of the invention to provide a thin-film magnetic head and a method of manufacturing the same and a thin-film magnetic head material and a method of manufacturing the same for preventing damage and a reduction in performance characteristics of the reproducing head.
In addition to the first object, it is a fourth object of the invention to provide a thin-film magnetic head and a method of manufacturing the same and a thin-film magnetic head material and a method of manufacturing the same for reducing the thickness of an overcoat layer.
A thin-film magnetic head of the invention comprises: a reproducing head including: a magnetoresistive element; and a first shield layer and a second shield layer for shielding the magnetoresistive element, portions of the first and second shield layers located on a side of a medium facing surface that faces toward a recording medium being opposed to each other with the magnetoresistive element in between; and a recording head including: a first magnetic layer and a second magnetic layer magnetically coupled to each other each of which includes at least one layer, the first and second magnetic layers including magnetic pole portions opposed to each other and placed in regions on a side of the medium facing surface; a gap layer placed between the pole portions of the first and second magnetic layers; and a thin-film coil at least part of which is placed between the first and second magnetic layers and insulated from the first and second magnetic layers. The second shield layer includes: a first portion placed in a region including a region facing the thin-film coil; a second portion connected to a surface of the first portion facing the coil and placed on a side of the first shield layer; and a third portion connected to the second portion and facing the first shield layer, the MR element being placed between the third portion and the first shield layer; and the second shield layer also functions as the first magnetic layer. The at least part of the thin-film coil is placed on a side of the second portion of the second shield layer.
A method of the invention is provided for manufacturing a thin-film magnetic head comprising: a reproducing head including: a magnetoresistive element; and a first shield layer and a second shield layer for shielding the magnetoresistive element, portions of the first and second shield layers located on a side of a medium facing surface that faces toward a recording medium being opposed to each other with the magnetoresistive element in between; and a recording head including: a first magnetic layer and a second magnetic layer magnetically coupled to each other each of which includes at least one layer, the first and second magnetic layers including magnetic pole portions opposed to each other and placed in regions on a side of the medium facing surface; a gap layer placed between the pole portions of the first and second magnetic layers; and a thin-film coil at least part of which is placed between the first and second magnetic layers and insulated from the first and second magnetic layers. The second shield layer includes: a first portion placed in a region including a region facing the thin-film coil; a second portion connected to a surface of the first portion facing the coil and placed on a side of the first shield layer; and a third portion connected to the second portion and facing the first shield layer, the MR element being placed between the third portion and the first shield layer; and the second shield layer also functions as the first magnetic layer. The at least part of the thin-film coil is placed on a side of the second portion of the second shield layer. The method includes the steps of: forming the first portion of the second shield layer; forming at least part of the thin-film coil such that the at least part of the coil is placed on the first portion and insulated from the first portion; forming the second portion of the second shield layer such that the second portion is located on the side of the at least part of the coil and connected to the surface of the first shield layer facing the coil; forming the first shield layer on a side of the second portion; forming the magnetoresistive element on an insulating film formed on the first shield layer; forming the third portion of the second shield layer on an insulating film formed on the magnetoresistive element; forming the gap layer on the third portion; and forming the second magnetic layer on the gap layer.
According to the thin-film magnetic head or the method of manufacturing the same of the invention, a thin-film magnetic head material comprising the first shield layer, the first and second portions of the second shield layer, and at least part of the thin-film coil is manufactured. In response to the customer""s requests, the third portion of the second shield layer, the magnetoresistive element, and the second magnetic layer may be formed in the material.
According to the head or the method of the invention, the second magnetic layer may be made up of a single layer.
According to the head or the method, the second shield layer may further include a fourth portion that is connected to a surface of the third portion facing the gap layer and defines a throat height. In this case, the second magnetic layer may be made of a single flat layer.
According to the head or the method, the thin-film coil may include a second layer portion located on a side of the third portion of the second shield layer.
According to the head or the method, a surface facing the magnetoresistive element of each of the first shield layer, the second portion of the second shield layer, and the at least part of the coil may be flattened.
According to the head or the method, the thin-film coil may include a second layer portion located on a side of the fourth portion of the second shield layer. In this case, an insulating layer may be further provided on a side of the third portion of the second shield layer, wherein a surface facing the second layer portion of each of the third portion and the insulating layer is flattened.
According to the head or the method, an insulating layer may be further provided between the gap layer and the second magnetic layer and defines a throat height.
According to the head or the method, a first insulating layer may be further provided along a surface of the thin-film coil and a second insulating layer may be provided to cover the first insulating layer.
According to the head or the method, an insulating layer may be further provided along surfaces of the first portion and the second portion of the second shield layer, wherein the first shield layer is separated from the second portion by the insulating layer.
According to the head or the method, an insulating layer made of an inorganic material may be further provided to cover the thin-film coil.
According to the head or the method, an insulating layer covering the first portion of the second shield layer may be further provided and a surface of the insulating layer facing the coil may be flattened.
According to the head or the method, an insulating layer may be provided, the insulating layer having a concave portion in a region corresponding to the first portion of the second shield layer, wherein the first portion is formed in the concave portion.
A thin-film magnetic head material of the invention is used for manufacturing a thin-film magnetic head comprising: a reproducing head including: a magnetoresistive element; and a first shield layer and a second shield layer for shielding the magnetoresistive element, portions of the first and second shield layers located on a side of a medium facing surface that faces toward a recording medium being opposed to each other with the magnetoresistive element in between; and a recording head including: a first magnetic layer and a second magnetic layer magnetically coupled to each other each of which includes at least one layer, the first and second magnetic layers including magnetic pole portions opposed to each other and placed in regions on a side of the medium facing surface; a gap layer placed between the pole portions of the first and second magnetic layers; and a thin-film coil at least part of which is placed between the first and second magnetic layers and insulated from the first and second magnetic layers. The second shield layer includes: a first portion placed in a region including a region facing the thin-film coil; a second portion connected to a surface of the first portion facing the coil and placed on a side of the first shield layer; and a third portion connected to the second portion and facing the first shield layer, the MR element being placed between the third portion and the first shield layer; and the second shield layer also functions as the first magnetic layer. The at least part of the thin-film coil is placed on a side of the second portion of the second shield layer. The thin-film magnetic head material comprises: the first shield layer; the first portion of the second shield layer; the second portion of the second shield layer; and the at least part of the thin-film coil located on the side of the second portion.
A method of the invention is provided for manufacturing a thin-film magnetic head material used for manufacturing a thin-film magnetic head comprising: a reproducing head including: a magnetoresistive element; and a first shield layer and a second shield layer for shielding the magnetoresistive element, portions of the first and second shield layers located on a side of a medium facing surface that faces toward a recording medium being opposed to each other with the magnetoresistive element in between; and a recording head including: a first magnetic layer and a second magnetic layer magnetically coupled to each other each of which includes at least one layer, the first and second magnetic layers including magnetic pole portions opposed to each other and placed in regions on a side of the medium facing surface; a gap layer placed between the pole portions of the first and second magnetic layers; and a thin-film coil at least part of which is placed between the first and second magnetic layers and insulated from the first and second magnetic layers. The second shield layer includes: a first portion placed in a region including a region facing the thin-film coil; a second portion connected to a surface of the first portion facing the coil and placed on a side of the first shield layer; and a third portion connected to the second portion and facing the first shield layer, the MR element being placed between the third portion and the first shield layer; and the second shield layer also functions as the first magnetic layer. The at least part of the thin-film coil is placed on a side of the second portion of the second shield layer. The method includes the steps of: forming the first portion of the second shield layer; forming at least part of the thin-film coil such that the at least part of the coil is placed on the first portion and insulated from the first portion; forming the second portion of the second shield layer such that the second portion is located on the side of the at least part of the coil and connected to the surface of the first shield layer facing the coil; and forming the first shield layer on a side of the second portion.
According to the thin-film magnetic head material or the method of manufacturing the same of the invention, the thin-film magnetic head material comprising the first shield layer, the first and second portions of the second shield layer, and at least part of the thin-film coil is manufactured. In response to the customer""s requests, the third portion of the second shield layer, the magnetoresistive element, and the second magnetic layer may be formed in the material.
According to the head material or the method, a surface facing the magnetoresistive element of each of the first shield layer, the second portion of the second shield layer, and the at least part of the coil may be flattened.
According to the head material or the method, a first insulating layer may be further provided along a surface of the thin-film coil and a second insulating layer may be provided to cover the first insulating layer.
According to the head material or the method, an insulating layer may be further provided along surfaces of the first portion and the second portion of the second shield layer, wherein the first shield layer is separated from the second portion by the insulating layer.
According to the head material or the method, an insulating layer made of an inorganic material may be further provided to cover the thin-film coil.
According to the head material or the method, an insulating layer covering the first portion of the second shield layer may be further provided and a surface of the insulating layer facing the coil may be flattened.
According to the head material or the method, an insulating layer may be provided, the insulating layer having a concave portion in a region corresponding to the first portion of the second shield layer, wherein the first portion is formed in the concave portion.
Other and further objects, features and advantages of the invention will appear more fully from the following description.